Solute carrier family 30, member 10, ZnT10. Manganese efflux transporteer of 485 aas and 6 TMSs in a 4 + 2 TMS arrangement with two long hydrophilic regions between residues 135 and 240, and residues 300 and 485 (Nishito et al. 2016). Homozygous mutations lead to the development of familial manganese Mn2+-induced
parkinsonism; it is a cell surface-localized Mn2+ efflux
transporter, and parkinsonism-causing mutations block its trafficking and efflux activity. Residues in the
transmembrane and C-terminal domains together confer optimal Mn2+ transport capability (Zogzas et al. 2016). Residues involved in Mn2+ binding in the transmembrane domain have been identified, and they differ in position and nature from the Zn2+ binding site in Zn2+ transporting members of the CDF family (Zogzas and Mukhopadhyay 2018). Loss of ZnT10 expression caused by autosomal mutations in the ZnT10 gene leads to hypermanganesemia in multiple organs (Levy et al. 2019). The cellular transport of Mn2+ is coupled to a reciprocal movement of Ca2+. Replacing a single asparagine residue in ZnT10 (Asn-43) with threonine (ZnT10 N43T) converted the Mn2+/Ca2+ exchanger into an uncoupled channel permeable to both Ca2+ and Mn2+ (Levy et al. 2019).

The plasma membrane zinc efflux system, ZnT-1, of 485 aas and 6 predicted TMSs with a large histidine-rich intracellular loop between TMSs 4 and 5 and intracellular C- and N-termini (Balesaria and Hogstrand 2006).

Mammary epithelia/brain Zn2+ transporter ZnT4 (the cause of inherited zinc deficiency in the lethal milk (lm) syndrome of mice, due to a nonsense mutation at codon 297 (arg) in the ZnT4 gene) (Huang and Gitschier, 1997).

Metal tolerance protein 4, MTP4, of 386 aas. Exports Zn2+ and Cd2+ (Migocka et al. 2015). MTP1 transports the same two ions but is less restrictive with respect to the tissues in which the protein is synthesized.

Co2+ resistance protein, DmeF, of 382 aas and 6 TMSs. Co2+ export appears to be its dominant physiological function, but it may also export other heavy metal ions such as Zn2+ and Cd2+ (Munkelt et al. 2004).

Zn2+/Cd2+/Hg2+/Fe2+:H+ antiporter, YiiP or FieF (Chao and Fu, 2004b; Grass et al., 2005; Wei et al., 2004; Wei and Fu, 2006). The structure (3.8 Å resolution) reveals a homodimer interconnected at the cytoplasmic domain through four Zn2+ ions. A 6 TMS bundle features of a tetrahedral Zn2+ binding site (Lu and Fu, 2007). The gated water access to the transport site enables a stationary proton gradient
to facilitate the conversion of zinc-binding energy to the kinetic power stroke of a vectorial zinc
transport (Gupta et al. 2014).

Putative magnetosome membrane iron transporter, MamB. Forms a heterodimeric stable complex with MamM which stabilizes MamB. MamB also interacts with other proteins including the PDZ1 domain of MamE (Q6NE61). Both MamB and MamM are essential for magnetite biomineralization and are involved in several steps in magnetosome formation, but only MamB is essential for formation of magnetosome membrane vesicles (Uebe et al. 2011). Implicated in iron uptake due to homology with other CDF transporters.

Putative magnetosome membrane iron transporter, MamM. Forms a heterodimeric stable
complex with MamB which it stabilizes. MamB; see 2.A.4.7.3) also interacts with other
proteins including the PDZ1 domain of MamE (Q6NE61). Both MamB and
MamM are essential for magnetite biomineralization and are involved in
several steps in magnetosome formation, but only MamB is essential for
formation of magnetosome membrane vesicles (Uebe et al. 2011). Implicated in iron uptake due to homology with other CDF transporters. Most CDF proteins contain two domains, the cation transporting transmembrane domain and the regulatory cytoplasmic C-terminal domain (CTD). A MamM M250P mutation that is synonymous with the disease-related mutation L349P of the human CDF protein, ZnT-10 causes severe structural changes in its CTD, resulting in abnormally reduced function.Thus, the CTD fold is critical for the CDF proteins' proper function and suggest that the CDF cytoplasmic domain is a CDF regulatory element (Barber-Zucker et al. 2016).

Cobalt/zinc resistance protein B, CzrB, of 291 aas and 6 TMSs. It has a cytosolic extramembranal C-terminus. This 92-residue
fragment may function independently of the full-length integral membrane
protein. X-ray analyses of this fragment to 2.2 A resolution with and 1.7 A without zinc
ions have been solved. The former has at least two zinc ions bound per monomer (Höfer et al. 2007). Full-length variants of CzrB in the apo and zinc-loaded states were generated by homology modeling
with the Zn2+/H+ antiporter YiiP. The model suggests a way in which zinc
binding to the cytoplasmic fragment creates a docking site to which a
metallochaperone can bind for delivery and transport of zinc. A proposal was advanced that it functions as a
metallochaperone and regulates the zinc-transporting activity of
the full-length protein. The latter requires that zinc binding becomes
uncoupled from the creation of a metallochaperone-docking site on CzrB (Cherezov et al. 2008).

Zn2+ transporter, TMEM163, of 289 aas and 6 TMSs. Interacts with TrpML1 (TC# 1.A.5.3.1) to influence Zn2+ homeostasis, possibly by pumping out Zn2+. May be involved in the human lipid storage disorder, mucolipidosis type IV (MLIV), caused by Zn2+ overload (Cuajungco et al. 2014). TMEM163 is found in synaptic vesicles where it is called SV31 (Burré et al. 2007). It plays a role in Zn2+ uptake into lysosomes (Cuajungco and Kiselyov 2017).